Apparatus for screening pulverized material.



Patented May 28, mm.

T. A. EDISON. APPARATUS FOR SCREENING PULVERIZED MATERIAL.

(Application filed June 29, 1897.)

(No Model.)

I'NVENTOR a J 51" ATTORNEYS my WITNESSES NITED STATES LLATENT Ormcn.

THOMAS A. EDISON, OF LLEVVELLYN PARK, NEW JERSEY.

APPHATUS FOR SCREENING PULVERIZED MATERIAL.

SPECIFICATION forming part of Letters Patent No. 675,057, dated May 28, 1901.

Application filed June 29, 1897. b'erial No. 642,812. (No model.)

To :LZZ whom it may concern: to employ inclined stationary screens on ac- Be it known that I, THOMAS A. EDISON, a count of their small screening capacity. The citizen of the United States, residing at Llewdifficulty, I have discovered, has been due to 55 ellyn Park, in the county of Essex and State the accelerated speed of the particles, arising of New Jersey, have invented a certain new from the fact that a screen which has incliand useful Improvement in Apparatus for nation enough to cause the material to flow ScreeningPulverized Material, (Case No.978,) does a large percentage of the work in the of which the following is a specification. first-foot of its surface and the rest of the sur- 60 The object I have in view is to produce an face is largely ineffective. My screensecto apparatus for screening pulverized material tions being exceedingly short-for example, which will result in largely increasing the two feet-the material does not accelerate screening capacity for the same area ofscreengreatly in speed before its movement is arsurface and by which little or no clogging of rested. I also make the inclination of the 65 the screen-surface will occur and the wear screens as small as the nature of the material will be reduced to a minimum. will admit and cause a free flow by gravity.

In carrying out my invention I place in a For dry ore I have found an angle of forty vertical stack, one above the other, a series degrees to be sutficient; but, generally speakof short stationary inclined soreen-surfaces ing, the less the inclination which can be em- 70 having slotted openings running in the direcployed the slower will be the speed and the tion of flow of the material. The pulverized greater will be the screening elfect. The inmaterial runs by gravity over these screeneffectiveness of stationary inclined screens surfaces in an exceedingly thin but uniform heretofore has led to the almost universal stream, and its motion is arrested before it adoption of rotating or vibrating screens; but 75 is delivered to each screen. The material is these have, compared with my screens, asmall fed to the top screen by a roller-feed, which screening capacity, take considerable power delivers to the entire width of the screen-surto operate them, are expensive to build, and face a stream of material having a uniform have great wear. This great wearis due to the thickness of only one or two particles. The weight of the material pressing on the screen- 8o inclination of the screen-surface is such that surface, which also results in the rapid clogthe material will run freely overitby gravity, ging of the screen by the jamming of partisome of the finer particles passing through cles in the openings. With my screens the the slots. The screen is, however, short in wear is not only slight, but-the clogging is length, so that the material does not acquire reduced to a' minimum, and it is only after 85 a very great velocity before reaching the lower considerable use that any cleaning becomes 3 5 end of the screen. After leaving the first necessary.

screen the motion of the material is arrested, In the accompanying drawings, forming a and it is delivered with a slow rate of speed part hereof, Figure 1 is an elevation and parby gravity to a second and similar inclined tial section showing two of the screen-stacks; 0 screen, and so on, successively over the full and Fig. 2 is an elevation, at right angles to 40 number or screens in the stack. I have found Fig.1, of one of the stacks, a door in the stack thatin passing pulverized material over a st-abeing open to show the slotted screen-surface. tionary inclined screen-surface the particles A is an inclosed stack, which may be of any soon acquire such a speed and bounding mosuitable height and may be provided with a 5 tion that the screen-surface becomes ineffectlarge number of screens, three of such screens ive, but that if the screen-surface is made in being shown for illustration. At the top of short lengths or sections and the material is the stack is a hopper B, from which the maarrested in its motion and delivered to each terial is delivered by a roller 0, having a successive section ataslow rate of speed stalength equal to the width of the screen-sur- 10c tionary inclined screen-surfaces can be emface. The material is fed out over the top of ployed to advantage and will have a large the roller, the thickness of the stream being screening capacity. regulated by an adjustable gate a, so that a It has notheretofore been found practicable stream having a uniform thickness of one or two particles will pass over the top of the roller. This stream will be delivered at one side of the stack upon a horizontal shelf b.

, This shelf becomes loaded with the pulverized material, and the falling stream striking the material on the shelf has its motion arrested and slides ofi of the shelf with a minimum speed upon. the first inclined screen D, which crosses to the other side of the stack. The screen D is a thin steel plate slotted in the direction of flow of the material, so that the particles may pass through the screen, notwithstanding their sliding motion down its surface. The screen D is supported in a suitable frame c, provided with hooks a at its upper end, which are hung over pins on the side of the stack, the lower end of the frame being removably supported by braces 01 or other suitable means. Opposite the screen D the stack is provided with a door E, which may be opened to give access to the screen and to permit it to be removed when worn and replaced by a similar screen without delay, or the door may be opened and the screen swung down into the position shown in dotted lines in Fig. 1 for cleaning it by a brush.

The material which passes through the screen D falls upon an inclined board or metal plate F, down which it runs to the discharge. The material which passes over the screen D is discharged at the lower end of the screen upon a horizontal shelf 6, which arrests its mot-ion and from which it passes to an inclined board or plate G placed directly beneath the board or plate F. The board G is inclined in the opposite direction to the inclination of the screen D. This changes the direction of flow of the pulverized material and arrests its motion. The material is discharged from the plate G upon a horizontal shelf f, which again arrests the motion of the material and delivers it with a minimum speed to the second screen D. The screensurface D is similar to the screen-surface D and is supported in the same Way. It is inclined in the same direction as the screen D, but opposite to the board G,and hence changes the direction of flow of the material and arrests its motion. The material which passes through the screen D is received by an inclined board or plate F, similar to F, while the material which passes over the screen D is received by a horizontal shelf 6, similar to e, and passes over an inclined board or plate G, similar to G, when it is received by a horizontal shelf f, similar to f, and passes onto a screen D similar to the other screens. The material which passes through the screen D is received by an inclined board or plate F while the material which passes over the screen D enters a discharging-conduit H, provided with bafliing-plates g for arresting its motion. An adjoining screen-stack discharges the coarse material into the same conduit H. The material which passes through the screens is checked in its descent from the inclined boards F and F by horizontal shelves h h and is discharged from the board F into a discharging-conduit I, provided with baffleplates t'.

It will be observed that the direction of the flow of the material is changed in presenting it to each screen, and hence its motion is arrested. The arresting of the motion is best accomplished by delivering the material at the receiving end of each screen to the horizontal shelf and against the angle formed between the shelf and the side of the stack; but it will be understood that the arresting of the motion, however it is accomplished, is the purpose of this construction. It might be arrested by discharging directly upon the upper end of each screen; but this would result in the wear of the screens, and hence I prefer to discharge it into an angle where the material accum ulates and forms a wearing-surface of the material itself. Since the weight of the material in passing over the screens is very slight, the pressure upon the screen-surface is a minimum and the wear is exceedingly small. I have also found that scarcelyany clogging of these screen-plates occurs.

What I claim is 1. An improved screening apparatus comprising a series of short, stationary, inclined screen-sections each formed of a thin plate slotted in the direction of flow of the material, means for causing the material to flow by gravity successively over the screen-sections, means for feeding material to the upper end of the upper screen-section in a thin, wide stream, and means for checking the velocity of the particles after they have passed over each screen-section except the last, substantially as set forth.

2. An improved screening apparatus comprising a series of short, stationary, inclined screen-sections each formed of a thin plate slotted in the direction of flow of the material, means for causing the material to flow by gravity successively over the screen-sections, means for feeding material to the upper end of the upper screen-section in athin, wide stream, and a checking-shelf below each of the screen-sections except the last, by which the particles will be brought to rest after passing each screen-section except the last, substantially as set forth.

3. An improved screening apparatus comprising a series of short, stationary, inclined screen-sections each formed of a thin plate slotted in the direction of flow of the material, means for causing the material to flow by gravity successively over the screen-sections, means for feeding material to the upper end of the upper screen-section in athin, wide stream, and means for changing the direction of flow of the particles after they have passed each screen-section, whereby the particles will be brought to rest, substantially as set forth- 4. An improved screening apparatus comprising a series of short, stationary, inclined screen-sections each formed of a thin plate slotted in the direction of flow of the material, said sections being placed one above the other and inclining in the same direction, means for feeding material to the upper end of the upper screen-section in a thin, wide stream, and pairs of parallel imperforate plates arranged between the lower end of each screen-section except the last and the upper end of the next succeeding screen-section for conveying the tailings successively over the screen-sections and separating the screenings removed by the screen-sections, whereby the material after leaving each screen-section except the last Will be brought to rest by having its direction changed, substantially as set forth. 

